Recently implemented U.S. Department of Transportation (DOT) safety regulations for hazardous material delivery trucks performing metered delivery service require a radio remote safety shutdown system. The system must have a range of 300 feet and be capable in an emergency of closing the delivery truck's valve and shutting down the engine, which normally powers the fluid pump for discharge fluid from the vehicular tank. Such an emergency may be characterized by delivery problems such as unexpected fluid loss.
DOT regulations require delivery vehicles with a capacity less than 3500 gallons to have a “kill” button on a remote transmitter, allowing the operator to manually and remotely shutdown the valve and engine by pressing the kill button. Delivery vehicles with a capacity greater than 3500 must further have a “query” feature. The query feature is typically implemented using a controller programmed to trigger a shutdown system after a specified time interval (for example, 5 minutes) unless it receives input from the operator, such as by pressing a button on the remote transmitter. The query feature for larger capacity vehicles anticipates the possibility that transmitter batteries may fail or the operator may not comply with the requirement to carry the transmitter at all times. The query feature is not required, however, on vehicles with a capacity under 3500 gallons of product, which constitute the majority of delivery vehicles.
DOT regulations require that remote safety shutdown systems be tested daily to assure proper operation. A working transmitter carried by the delivery operator must be capable of transmitting to the receiver at all times during the delivery cycle. Safety systems also typically provide some type of “low battery” indication on the transmitter.
Many of the existing systems have only the minimum required functionality, which, for trucks with capacities of less than 3500 gallons, is limited to a kill button. Because a kill button function is only used in an emergency, an operator may be less inclined to keep the transmitter nearby while performing routine delivery duties. This increases the likelihood that the operator will neglect the transmitter, such as by leaving the transmitter in the truck or allowing the batteries to run down. Nothing compels operators to comply with DOT regulations by carrying an operational transmitter, and operators may be free to deliver product without using the transmitter.
Although not required for DOT, the query feature may be used on delivery vehicles having less than a 3500 gallon capacity. The query feature is typically initiated when the operator sets the parking brake of the vehicle while the engine is running. Once activated, the operator must repetitively reset the timer prior to expiration of a given time interval. One perceived problem with such a feature is that the query feature may sometimes be activated when it is not needed, such as when the truck is being warmed up with the parking brake on prior to a delivery run. Then the operator must repetitively reset the timer in accordance with the query feature to prevent the engine from being disabled, even though no product is being transferred.
Some safety system manufacturers have addressed this problem by internally tying the query timer electronically to the activation of the power take off (PTO), which is when the query feature is more likely necessary. The PTO is a power drive shaft that drives the pump on the fluid delivery system, which means the fluid delivery system is likely in use. Tying the system to such a function ensures that the query timer will be activated only when both the parking brake is on and the pump is running. This configuration will not interfere with the operator's ability to idle the vehicle with the parking brake set, such as to warm up the vehicle on a cold morning.
Although such a configuration may be an improvement on the minimum required functionality, more can be done to ensure operator compliance when only a kill button is used, and the prior art has failed to identify or implement such further measures.
The disadvantages of the prior art are overcome by the present invention, and an improved safety shutdown system suitable for hazardous material delivery trucks is disclosed.